A3064. Hall Effect Gear Tooth Sensor IC, AC Coupled. Discontinued Product

Transcription

1 A364 Hall Effect Gear Tooth Sensor IC, AC Coupled Discontinued Product These parts are no longer in production The device should not be purchased for new design applications. Samples are no longer available. Date of status change: October 31, 25 Recommended Substitutions: For new customers and applications, refer to the A1421LK. NOTE: For detailed information on purchasing options, contact your local Allegro field applications engineer or sales representative. Allegro MicroSystems, Inc. reserves the right to make, from time to time, revisions to the anticipated product life cycle plan for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.

2 X X 364 The A364LKA ac-coupled Hall-effect gear-tooth sensor IC is a monolithic integrated circuit that switches in response to changing differential magnetic fields created by moving ferrous targets. This device is ideal for use in non-zero-speed, gear-tooth-based speed, position, and timing applications such as in anti-lock braking systems, transmissions, and crankshafts. Data Sheet B V CC SUPPLY OUTPUT GROUND ABSOLUTE IMUM RATINGS at T A = +25 C Supply Voltage, V CC V Reverse Battery Voltage, V RCC V Magnetic Flux Density, B... Unlimited Output Off Voltage, V OUT V Output Current, I OUT ma Package Power Dissipation, P D... 5 mw Operating Temperature Range, T A C to +15 C Storage Temperature Range, FILTER FILTER Dwg. PH-11-1 Pinning is shown viewed from branded side. T S C to +17 C When coupled with a back-biasing magnet, the device can be configured to turn on or off with the leading or trailing edge of a geartooth or slot. Changes in fields on the magnet face caused by a moving ferrous mass affect the two Hall transducers and are differentially amplified by on-chip electronics. This differential design provides immunity to radial vibration within the device s operating air gap. Steady-state magnet and system offsets are eliminated using an on-chip differential band-pass filter. This filter also provides relative immunity to interference from RF and electromagnetic sources. The on-chip temperature compensation and Schmitt trigger circuitry minimizes shifts in effective working air gaps and switch points over temperature, allowing operation to low frequencies over a wide range of air gaps and temperatures. Each Hall-effect digital Integrated circuit includes a voltage regulator, two quadratic Hall-effect elements, temperature compensating circuitry, a low-level amplifier, band-pass filter, Schmitt trigger, and an open-collector output driver. The on-board regulator permits operation with supply voltages of 4.5 to 24 volts. The output stage can easily switch 2 ma over the full frequency response range of the device and is compatible with bipolar and MOS logic circuits. The device is packaged in a 5-pin plastic SIP. FEATURES For Sensing Motion of Ferrous Targets Wide Operating Temperature Range Operation to 3 khz Resistant to EMI Large Effective Air Gap 4.5 V to 24 V Operation Output Compatible With All Logic Families Reverse Battery Protection Resistant to Physical Stress Always order by complete part number, e.g., A364LKA.

3 364 1 SUPPLY FUNCTIONAL BLOCK DIAGRAM REG X X + - OUTPUT 2 3 GROUND 4 5 FILTER FILTER Dwg. FH-8-1 ELECTRICAL CHARACTERISTICS over operating temperature and supply voltage range. Characteristic Symbol Test Conditions Min. Limits Typ. Max. Units Supply Voltage VCC Operating V Output Saturation Voltage V OUT(SAT) I OUT = 18 ma, B < B RP mv Output Leakage Current I OFF V OUT = 24 V, B > B OP 5. µa Supply Current ICC B < B RP 11 2 ma B > B OP 9.6 ma High-Frequency Cutoff f coh -3 db 3 khz Output Rise time tr V OUT = 12 V, R L = 82 Ω.4.2 µs Output Fall time tf V OUT = 12 V, R L = 82 Ω.18.3 µs MAGNETIC CHARACTERISTICS over operating temperature and supply voltage range. Limits Characteristic Symbol Test Conditions Min. Typ. Max. Units Operate Point BOP Output switches on to off G Release Point BRP Output switches off to on G Hysteresis Bhys B OP - B RP G NOTES: 1. Magnetic switch points are specified as the difference in magnetic fields at the two Hall elements. 2. As used here, negative flux densities are defined as less than zero (algebraic convention). 3. Typical values are at T A = 25 C and V CC = 12 V gauss (G) is exactly equal to.1 millitesla (mt) Northeast Cutoff, Box 1536 Worcester, Massachusetts (58) Copyright 21 Allegro MicroSystems, Inc.

4 TYPICAL OPERATING CHARACTERISTICS SWITCH POINTS V = 12 V CC DIFFERENTIAL FLUX DENSITY IN GAUSS 2 OPERATE POINT 1 RELEASE POINT AMBIENT TEMPERATURE IN C 15 Dwg. GH-56-1 OUTPUT SATURATION VOLTAGE 3 2 I OUT = 18 ma V CC = 12 V I OUT = 18 ma T = +25 C A SATURATION VOLTAGE IN mv 2 1 SATURATION VOLTAGE IN mv AMBIENT TEMPERATURE IN C SUPPLY VOLTAGE IN VOLTS Dwg. GH-29-6 Dwg. GH

5 364 TYPICAL OPERATING CHARACTERISTICS SUPPLY CURRENT 2 2 V CC = 24 V SUPPLY CURRENT IN ma 1 5 B > B OP B < B RP SUPPLY CURRENT IN ma 1 5 B < B RP B > B OP T = +25 C A AMBIENT TEMPERATURE IN C SUPPLY VOLTAGE IN VOLTS Dwg. GH-28-9 Dwg. GH-31-3 APPLICATIONS INFORMATION The A364LKA is a versatile high-precision differential sensing device that can be used in a wide range of applications. Careful choice of the sensor IC, target material and shape, magnet material and shape, and assembly techniques enables large working air gaps and high switch-point accuracy over the system operating temperature range. Magnet Biasing. To sense moving non-magnetized ferrous targets, these devices must be back biased by mounting the unbranded side on a small permanent magnet. Either magnetic pole (north or south) can be used. The devices can be used without a back-biasing magnet. For example, the device can be used to detect a rotating ring magnet such as those found in brushless dc motors or in speed sensing applications. OUTPUT VOLTAGE +V Figure 1 TYPICAL TRANSFER CHARACTERISTIC B RP B OP V CC Device Operation. These sensor ICs each contain two Hall transducers (E1 and E2) that are used to sense a magnetic field differential across the face of the IC (see Element Location drawing). Referring to the Typical Transfer Characteristic (Figure 1), the trigger switches the output off (output high) when B E1 - B E2 > B OP and switches the output on (output -B V OUT(SAT) FLUX DENSITY +B Dwg. GH Northeast Cutoff, Box 1536 Worcester, Massachusetts (58) 853-5

6 APPLICATIONS INFORMATION (cont d) 364 low) when B E1 - B E2 < B RP. The difference between B OP and B RP is the hysteresis of the device. Figure 2 LEADING EDGE TRAILING EDGE Note that powering up in the absence of a differential magnetic field (less than the device B OP and higher than the device B RP ) will allow an indeterminate output state. The correct output state is warranted after the first excursion beyond B OP or B RP. E2 GEAR NORTH E1 DIRECTION OF ROTATION Figure 2 relates the output state of a back-biased sensor IC, with switching characteristics shown in Figure 1, to the target gear profile and position. Assume a north pole back-bias configuration (equivalent to a south pole at the face of the device). The motion of the gear produces a phase-shifted field at E1 and E2 (Figure 2(a)); internal conditioning circuitry subtracts the fields at the two elements (Figure 2(b)); this differential field is band-pass filtered to remove dc offset components and then fed into a Schmitt trigger; the Schmitt trigger switches the output transistor at the thresholds B OP and B RP. As shown (Figure 2(c)), the IC output is low whenever E2 faces a (ferrous) gear tooth and element E1 faces air. The output is high when element E1 faces air and E2 faces a ferrous target. B & B E1 E2 B B E1 E2 V OUT 43 G 415 G 15 G B OP= +15 G G B RP= G -15 G SOUTH (a) (b) (c) AC-Coupled Operation. Steady-state magnet and system offsets are eliminated using an on-chip differential bandpass filter. The lower frequency cut-off of this patented filter is set using an external capacitor, the value of which can range from.1 µf to 1 µf. The high-frequency cut-off of this filter is set at 3 khz by an internal integrated capacitor. V OUT(SAT) 1 k OUTPUT DUTY CYCLE 5% Figure 3 Dwg. WH-3-3 The differential structure of this filter improves the ability of the IC to reject single-ended noise on the ground or supply line and, as a result, makes it more resistant to radio-frequency and electromagnetic interference typically seen in hostile remote-sensing environments. This filter configuration also increases system tolerance to capacitor degradation at high temperatures, allowing the use of an inexpensive external ceramic capacitor. Low-Frequency Operation. Low-frequency operation of the device is set by the value of an external capacitor. Ideally, the differential flux density range (determined by the applied target) vs. air gap assumes a perfect sinusoidal input. Figure 3 provides the low-frequency cut-off (-3 db point) of the filter as a function of capacitance value. This information should be used with care. In reality, when used with gear teeth, LOW-FREQUENCY CUTOFF IN Hz CAPACITANCE IN µf Dwg. GH

7 364 APPLICATIONS INFORMATION (cont d) the teeth create transitions in the magnetic field that have a much higher frequency content than the basic rotational speed of the target. This allows the device to work with speeds much lower than those indicated by the graph for a given capacitor value. Capacitor Characteristics. The major requirement for the external capacitor is its ability to operate in a bipolar (nonpolarized) mode. Another important requirement is the low leakage current of the capacitor (equivalent parallel resistance should be greater than 5 kω). To maintain proper operation with frequency, capacitor values should be held to within ±3% over the operating temperature range. The commonly available Z5U ceramic capacitor temperature code should not be used in this application. ACTIVE AREA DEPTH.165".42 mm NOM Figure 4 ELEMENT LOCATIONS (±.5 [.13 mm] die placement) A E1.87" 2.2 mm.83" 2.1 mm E2.75" 1.91 mm Magnet Selection. The A364LKA can be used with a wide variety of commercially available permanent magnets. The selection of the magnet depends on the operational and environmental requirements of the sensing system. For systems that require high accuracy and large working air gaps or an extended temperature range, the usual magnet material of choice is rare-earth samarium cobalt (SmCo). This magnet material has a high energy product and can operate over an extended temperature range. For systems that require low-cost solutions for an extended temperature range, AlNiCo 8 can be used. Due to its relatively low energy product, smaller operational air gaps can be expected. Neodymium iron boron (NeFeB) can be used over moderate temperature ranges when large working air gaps are required. Of these three magnet materials, AlNiCo 8 is the least expensive by volume and SmCo is the most expensive. Extensive applications information for Hall-effect devices is available in: Hall-Effect IC Applications Guide, Application Note 2771; Hall-Effect Devices: Soldering, Gluing, Potting, Encapsulating, and Lead Forming, Application Note ; Soldering of Through-Hole Hall-Sensor Dervices, Application Note 2773; and Soldering of Surface-Mount Hall-Sensor Devices, Application Note All are provided in Allegro Electronic Data Book, AMS-72. or at BRANDED SURFACE Allegro Dwg. MH-7E Northeast Cutoff, Box 1536 Worcester, Massachusetts (58) 853-5

8 364 CRITERIA FOR DEVICE QUALIFICATION All Allegro devices are subjected to stringent qualification requirements prior to being released to production. To become qualified, except for the destructive ESD tests, no failures are permitted. Qualification Test Test Method and Test Conditions Test Length Samples Comments Biased Humidity (HAST) JESD22-A11, 2 hrs 32 VCC = V OUT = 12 V RH = 85% 116 pcs at T A = 25 C 116 pcs at T A = 15 C High-Temperature JESD22-A18, 2 hrs 146 VCC = V OUT = 12 V Operating Life (HTOL) T J 19 C 116 pcs at T A = 25 C 3 pcs at T A = 15 C Accelerated HTOL T A = 175 C, T J 19 C 5 hrs 5 V CC = V OUT = 7.5 V Autoclave, Unbiased JESD22-A12, Condition C, 192 hrs 77 T A = 121 C at 15 psig Solder Heat 22 High-Temperature MIL-STD-883, Method 18, 2 hrs 77 (Bake) Storage Life T A = 17 C Temperature Cycle MIL-STD-883, Method 11, 2 cycles 153 (unbiased) +25 C to +15 C ESD, MIL-STD-883, Method 315 Pre/Post 3 per Test to failure, Human Body Model Reading test All leads > 2 kv The products described herein are manufactured under one or more of the following U.S. patents: 5,45,92; 5,264,783; 5,442,283; 5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319; 5,65,719; 5,686,894; 5,694,38; 5,729,13; 5,917,32; and other patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro products are not authorized for use as critical components in life-support appliances, devices, or systems without express written approval. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringements of patents or other rights of third parties that may result from its use. 7

9 364 Dimensions in Inches (controlling dimensions) Dimensions in Millimeters (for reference only) SEE NOTE SEE NOTE BSC Dwg. MH-1H in BSC Dwg. MH-1H mm Horizontal-Mount Lead Form (order A364LKA-TL).95 ± ± MIN FLAT Dwg. MH-15 in MIN FLAT Dwg. MH-15 mm NOTES: 1. Tolerances on package height and width represent allowable mold offsets. Dimensions given are measured at the widest point (parting line). 2. Exact body and lead configuration at vendor s option within limits shown. 3. Height does not include mold gate flash. 4. Recommended minimum PWB hole diameter to clear transition area is.35 (.89 mm). 5. Where no tolerance is specified, dimension is nominal. 6. Supplied in bulk pack (5 pieces per bag) Northeast Cutoff, Box 1536 Worcester, Massachusetts (58) 853-5